LED lighting technology is rapidly developing to replace traditional incandescent and fluorescent lighting. LED tube lamps are mercury-free in comparison with fluorescent tube lamps that need to be filled with inert gas and mercury. Thus, it is not surprising that LED tube lamps are becoming a highly desired illumination option among different available lighting systems used in homes and workplaces, which used to be dominated by traditional lighting options such as compact fluorescent light bulbs (CFLs) and fluorescent tube lamps. Benefits of LED tube lamps include improved durability and longevity and far less energy consumption. Therefore, when taking into account all factors, they would typically be considered as a cost effective lighting option.
Typical LED tube lamps have a lamp tube, a circuit board disposed inside the lamp tube with light sources being mounted on the circuit board, and end caps accompanying a power supply provided at two ends of the lamp tube with the electricity from the power supply transmitting to the light sources through the circuit board. However, existing LED tube lamps have certain drawbacks. For example, the typical circuit board is rigid and allows the entire lamp tube to maintain a straight tube configuration when the lamp tube is partially ruptured or broken, and this gives the user a false impression that the LED tube lamp remains usable and is likely to cause the user to be electrically shocked upon handling or installation of the LED tube lamp.
Conventional circuit design of LED tube lamps typically doesn't provide suitable solutions for complying with relevant certification standards. For example, since there are usually no electronic components in a fluorescent lamp, it's fairly easy for a fluorescent lamp to be certified under EMI (electromagnetic interference) standards and safety standards for lighting equipment as provided by Underwriters Laboratories (UL). However, there are a considerable number of electronic components in an LED tube lamp, and therefore consideration of the impacts caused by the layout (structure) of the electronic components is important, resulting in difficulties in complying with such standards.
Further, the driving of an LED uses a DC driving signal, but the driving signal for a fluorescent lamp is a low-frequency, low-voltage AC signal as provided by an AC powerline, a high-frequency, high-voltage AC signal provided by a ballast, or even a DC signal provided by a battery for emergency lighting applications. Since the voltages and frequency spectrums of these types of signals differ significantly, simply performing a rectification to produce the required DC driving signal in an LED tube lamp may not achieve the LED tube lamp's compatibility with traditional driving systems of a fluorescent lamp.
Moreover, when an LED tube lamp has an architecture with dual-end power supply and one end cap thereof is inserted into a lamp socket but the other is not, an electric shock situation could take place for the user touching the metal or conductive part of the end cap which has not been inserted into the lamp socket.
In the prior art, a solution of disposing a mechanical structure on the end cap for preventing electric shock is proposed. In this electric shock protection design, the connection between the external power and the internal circuit of the tube lamp can be cut off or established by the mechanical component's interaction/shifting when a user installs the tube lamp, so as to achieve the electric shock protection.
Currently, LED tube lamps used to replace traditional fluorescent lighting devices can be primarily categorized into two types. One is for ballast-compatible LED tube lamps, e.g., T-LED lamp, which directly replaces fluorescent tube lamps without changing any circuit on the lighting device; and the other one is for ballast by-pass LED tube lamps, which omit traditional ballast on their circuit and directly connect the commercial electricity to the LED tube lamp. The latter LED tube lamp is suitable for the new surroundings in fixtures with new driving circuits and LED tube lamps.
US Patent Application Publication No. 2005/0162850 discloses a flexible lighting device which includes an elongated flexible tube with a translucent tube shell and opposed tube ends and a flexible circuit board set in the tube so that it extends between the tube ends. The technical features disclosed in US 2005/0162850 are focused on the adoption and application of the flexible tube. A problem with the arrangements disclosed in US 2005/0162850, however, is that the electrical connection at circuit board ends are vulnerable to breakage. Thus, the lighting devices disclosed in US 2005/0162850 may suffer damage during manufacture, transport, and installation. Furthermore, US Patent Application Publication No. 2005/0162850 also discloses an external LED power supply and controller providing two separate control voltages to drive LEDs. A problem with the arrangements disclosed in US 2005/0162850, however, is that the external LED power supply and controller is too far away from the LED light source.
Also, when the LED power supply and controller is disposed outside an LED tube lamp, the power efficiency of the LED light sources inside the LED tube lamp will be limited and the parameter matching of the LED tube lamp is not good. Therefore, an internal LED power supply and controller inside an LED tube lamp could provide application flexibility of the LED tube lamp to meet different lighting needs.